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FAA Airline Transport Pilot Helicopter (135) Knowledge Test Practice Test

The ATH knowledge test concerns helicopter operations at the airline transport pilot level under Part 135. Practice questions sample aviation knowledge used in operational decisions, including altimeter settings, density-altitude effects, thunderstorm hazards, and responses to abnormal vibration or settling with power.

Exam overview

Exam providerFederal Aviation Administration
Exam codeATH
CategoryAviation

About the FAA Airline Transport Pilot Helicopter (135) Knowledge Test Exam

Sound helicopter judgment depends on connecting operating conditions with aircraft performance and safe procedures. Questions in this practice bank touch on pressure-altimeter interpretation, density altitude, and the limits these conditions place on helicopter performance. Weather scenarios address thunderstorm avoidance and the hazards of forecast icing, including why an apparent precipitation gap does not establish a safe route. Operational questions also cover the purpose of a takeoff alternate when applicable rules require one, compliance with Airworthiness Directives, and the roles of a governor and drive-system clutch during normal operation. Abnormal-condition scenarios ask you to recognize settling with power and respond appropriately to a developing vibration. Use these subjects to rehearse how a pilot interprets information, identifies hazards, and chooses a prudent operational response; the sampled topics describe this practice bank, not confirmed official test domains.

Sample Practice Questions

Review a selection from this exam's published US Practice Tests practice bank.

Question 1

When using a pressure altimeter, what does the altimeter setting generally do?

  1. ACorrects the altimeter indication for local atmospheric pressure so indicated altitude is more meaningful near the reporting location
  2. BMeasures the helicopter’s height above the nearest obstacle directly
  3. CCompensates for errors caused by rotor RPM changes
  4. DSets the helicopter’s maximum permissible operating weight
Show answerCorrect answer: A

Setting the reported pressure in the altimeter’s barometric window adjusts its indication for atmospheric pressure. The instrument still does not directly measure height above terrain or obstacles.

Question 2

For a helicopter operating near a thunderstorm, why is a visual gap in precipitation not sufficient evidence of a safe route?

  1. AThunderstorm hazards, including turbulence and wind shear, can extend beyond visible precipitation
  2. BHelicopters cannot fly in any cloud-free area near precipitation
  3. CA visual gap guarantees the aircraft will enter icing conditions
  4. DThunderstorms affect only fixed-wing aircraft at high altitude
Show answerCorrect answer: A

Severe turbulence, wind shear, hail, and other hazards can occur outside the visible precipitation core. A seemingly clear gap does not establish that a route is safe; pilots should maintain conservative separation and follow current weather guidance.

Question 3

For a helicopter operated under Part 135, what is the primary purpose of a takeoff alternate when required by the applicable operating rules?

  1. ATo provide a suitable airport for landing if the departure airport becomes unusable shortly after takeoff
  2. BTo replace the destination airport in the flight plan
  3. CTo satisfy the helicopter's scheduled maintenance requirements
  4. DTo permit takeoff with less fuel than otherwise required
Show answerCorrect answer: A

A takeoff alternate is a suitable location to which the aircraft can proceed if a landing at the departure airport is not possible after takeoff. The applicable requirements depend on the operation and conditions; an alternate does not replace destination planning or fuel rules.

Question 4

In a conventional helicopter, what is the purpose of the governor when the pilot is not manually changing engine power?

  1. ATo maintain rotor RPM within the selected operating range by adjusting engine output
  2. BTo hold the helicopter at a constant altitude
  3. CTo prevent the rotor from turning during engine start
  4. DTo adjust blade pitch automatically for every change in wind direction
Show answerCorrect answer: A

A governor senses rotor or engine speed and adjusts engine power to help maintain the selected RPM. It does not control altitude or replace the pilot’s control inputs.

Question 5

For a U.S. civil aircraft, what is the general purpose of complying with Airworthiness Directives applicable to that aircraft or its installed equipment?

  1. ATo satisfy mandatory corrective or inspection actions addressing an unsafe condition
  2. BTo obtain permission to use any maintenance provider
  3. CTo replace the aircraft flight manual with a maintenance log
  4. DTo make compliance optional once the aircraft has passed an annual inspection
Show answerCorrect answer: A

Airworthiness Directives are legally enforceable rules issued to address unsafe conditions. Applicable required actions must be completed in accordance with the AD and applicable regulations; a routine inspection does not automatically substitute for AD compliance.

Question 6

When a helicopter enters a settling-with-power condition, which combination most directly characterizes the condition?

  1. AHigh forward speed and low power with the rotor operating in clean air
  2. BA descent into the rotor's own disturbed air while power is applied and the helicopter has insufficient forward speed to escape
  3. CA rapid increase in rotor RPM caused by lowering collective
  4. DA tail-rotor failure accompanied by an immediate loss of directional control
Show answerCorrect answer: B

Settling with power, also called vortex ring state, can develop when the helicopter descends into its own recirculating rotor wake, commonly with power applied and inadequate translational airflow. Recovery generally requires leaving the disturbed airflow rather than simply increasing collective.

Question 7

A helicopter pilot is considering flight into forecast icing conditions. Which general principle should guide the decision?

  1. AProceed if the route is below the freezing level at departure
  2. BAvoid conditions for which the helicopter is not approved or adequately equipped, and follow applicable limitations
  3. CRely on rotor wash to prevent ice accumulation
  4. DContinue if visibility is unrestricted, because icing affects only fixed-wing aircraft
Show answerCorrect answer: B

Ice can degrade rotor and airframe performance and may create hazards even when visibility is good. The pilot should comply with aircraft limitations and avoid icing conditions unless the aircraft and operation are approved and equipped for them.

How to use this practice test

The free practice set draws up to 20 random questions from the 50-question ATH bank. Work through each item as an operational decision, then use the displayed results to identify concepts to revisit, such as weather risk, performance limits, or abnormal helicopter conditions.

Preparation tips

  • For altimeter questions, distinguish the pressure setting from indicated altitude and consider how a setting change affects the indication.
  • Practice explaining how density altitude affects rotorcraft performance, especially when evaluating available power and takeoff or landing margins.
  • For thunderstorm and icing scenarios, identify hazards beyond visible precipitation and decide when conditions warrant avoiding the route or delaying flight.
  • Review the purpose of a Part 135 takeoff alternate when required, and connect Airworthiness Directives to the continued airworthiness of the aircraft and installed equipment.
  • For abnormal-operation questions, distinguish settling with power from other performance problems and treat a new or increasing vibration as a condition requiring prompt assessment.
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